Air conditioner

ABSTRACT

An air conditioner includes a cooling heat exchanger configured to cool air, and a wet-state detection sensor attached to an air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water. The air outlet surface of the cooling heat exchanger is tilted by an angle with respect to a horizontal direction or is perpendicular to the horizontal direction, and the wet-state detection sensor is arranged at a position in an upper half area of the air outlet surface in a direction perpendicular to the horizontal direction. Alternatively, the wet-state detection sensor is arranged at a position of the air outlet surface in a high-temperature area in which the temperature is higher than an average temperature of the air outlet surface. In this case, the high-temperature area may be positioned within the upper half area of the air outlet surface.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2010-072526 filed on Mar. 26, 2010, the contents of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an air conditioner provided with a cooling heat exchanger and a wet-state detection sensor attached to the cooling heat exchanger.

BACKGROUND

Patent Document 1 (JP 11-198644A) and Patent Document 2 (JP 61-1526A) describe regarding a vehicle air conditioner in which a dew point temperature is calculated by using a temperature-humidity sensor, and it is determined whether dew condensation of an evaporator as a cooling heat exchanger is caused, and thereby a temperature control of the evaporator is performed. The temperature control of the evaporator is performed by controlling operation of a compressor of a refrigerant cycle, so that the evaporator temperature is increased as much as possible while it can prevent bad-smell from being generated from the evaporator.

More specifically, in the Patent Document 1, a temperature sensor and a humidity sensor are provided to detect respectively an air temperature and an air humidity at an air inlet side of the evaporator, and a wet state of the evaporator is determined based on the detected air temperature and the detected air humidity, such that an operation rate of a compressor is controlled based on the determined wet state.

In the Patent Document 2, a temperature sensor and a humidity sensor are provided to detect temperature and humidity in the vicinity of the evaporator, thereby controlling the evaporator temperature based on a dew point temperature calculated based on the detected temperature and the detected humidity. However, in a general air conditioner, the evaporator has a part in which condensation water gets dry easily, and a part which does not get dry easily, for example. The part in which condensation water gets dry easily is an upper part of the evaporator, when the evaporator is arranged by an angle with respect to a horizontal direction.

That is, when the evaporator is arranged by an angle with respect to the horizontal direction, the condensation water flows downwardly along the slant surface of the evaporator, and thereby the amount of the condensation water becomes smaller as the position of the evaporator is higher.

Furthermore, a temperature distribution is easily generated in the evaporator, and condensation water gets dry easily on the part of the evaporator, where the temperature is relatively high. The temperature distribution is easily caused on the evaporator, because a flow speed distribution of air passing through the evaporator is caused due to the inner shape of an air conditioning unit, or because the temperature of the refrigerant flowing in the evaporator is gradually increased as toward downstream in the refrigerant flow by absorbing heat from air.

However, in the air conditioner, even when the temperature sensor and the humidity sensor are arranged, it is difficult to accurately determine the wet state on the entire area of the evaporator.

For example, the bad-smell may be generated at a drying start time at which a part of condensation water begins to get dry in a part of a surface area of the evaporator.

SUMMARY

In view of the above matters, it is an object of the present invention to accurately detect a wet state in an entire area of a cooling heat exchanger.

It is another object of the present invention to prevent bad-smell from being generated in a cooling heat exchanger, while temperature of the cooling heat exchanger is increased as much as possible.

According to an aspect of the present invention, an air conditioner includes a cooling heat exchanger configured to cool air and having an air outlet surface from which air flows out of the cooling heat exchanger, and a wet-state detection sensor attached to the air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water. In the air conditioner, the air outlet surface of the cooling heat exchanger is tilted by an angle with respect to a horizontal direction or is perpendicular to the horizontal direction, and the wet-state detection sensor is arranged at a position in an upper half area of the air outlet surface in a top-bottom direction perpendicular to the horizontal direction. Thus, when the wet-state detection sensor detects that the detected position is wet, it is possible to detect that the entire area of the air outlet surface of the cooling heat exchanger is in a wet state, thereby accurately detecting the wet state in the entire area of the air outlet surface of the cooling heat exchanger. Therefore, it is possible to keep the entire area of the air outlet surface of the cooling heat exchanger at the wet state, thereby preventing bad-smell from being caused in the cooling heat exchanger.

According to another aspect of the present invention, an air conditioner, include a cooling heat exchanger configured to cool air and having an air outlet surface from which air flows out of the cooling heat exchanger, and a wet-state detection sensor attached to the air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water. The wet-state detection sensor is arranged at a position of the air outlet surface in a high-temperature area in which the temperature is higher than an average temperature of the air outlet surface. Thus, when the wet-state detection sensor detects that the detected position is in a wet state, it is possible to detect that the entire area of the air outlet surface of the cooling heat exchanger is in the wet state, thereby accurately detecting the wet state in the entire area of the air outlet surface of the cooling heat exchanger. Therefore, it is possible to keep the entire area of the air outlet surface at the wet state, thereby preventing bad-smell from being caused in the cooling heat exchanger.

For example, the upper half area of the air outlet surface of the cooling heat exchanger may have the high-temperature area in which the temperature is higher than the overage temperature of the air outlet surface, and the wet-state detection sensor may be arranged at a position in the high-temperature area. In this case, it is possible to more accurately detect a wet state in the entire area of the air outlet surface.

The wet-state detection sensor may be a moisture sensor adapted to detect moisture on the air outlet surface. Alternatively, the wet-state detection sensor may be a temperature-humidity sensor adapted to detect temperature and humidity of air flowing out of the air outlet surface. In this case, a control portion is adapted to calculate a dew point temperature based on a detected value of the wet-state detection sensor, and determines that the air outlet surface is wetted by the condensation water when a detected temperature of the wet-state detection sensor is lower than the dew point temperature.

According to another aspect of the present invention, in an air conditioner, a wet-state detection sensor is arranged at a position of the air outlet surface, in which a determination value for indicating an easy drying degree satisfies a predetermined condition so that the condensation water is easy to get dry. Therefore, it is possible to more accurately detect a wet state in the entire area of the air outlet surface.

For example, the cooling heat exchanger may be an evaporator in which refrigerant is evaporated thereby cooling air, and the evaporator may be one of components of a refrigerant cycle in which the refrigerant is circulated. In this case, operation of the refrigerant cycle is controlled based on a detected value of the wet-state detection sensor, so as to keep at a wet state on the air outlet surface of the evaporator.

Furthermore, an evaporator temperature sensor may be located in the air outlet surface of the evaporator at a low-temperature area where the temperature of the evaporator is lower than an average temperature, and the wet-state detection sensor is located in the air outlet surface of the evaporator at a high-temperature area where the temperature of the evaporator is higher than the average temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a schematic diagram showing an air conditioner for a vehicle according to a first embodiment;

FIG. 2 is a block diagram showing an electric controller of a vehicle air conditioner in FIG. 1;

FIG. 3 is a schematic sectional view showing a part of the vehicle air conditioner in FIG. 1;

FIG. 4 is a schematic perspective view showing a temperature distribution on an air outlet surface of an evaporator according to the first embodiment;

FIGS. 5A and 5B are a front view and a sectional view showing a part of the evaporator in FIG. 3;

FIG. 6 is a flowchart showing a control process performed by the vehicle air conditioner in the first embodiment;

FIG. 7 is a time chart showing control operation performed by the vehicle air conditioner, according to the first embodiment;

FIGS. 8A and 8B are a front view and a sectional view showing a part of an evaporator according to a modification example of the first embodiment; and

FIG. 9 is a schematic diagram showing a part of an air conditioner for a vehicle according to a second embodiment.

DETAILED DESCRIPTION

Embodiments will be described hereafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

First Embodiment

Next, a first embodiment and modification examples of the invention will be described with reference to FIGS. 1 to 8B. In the present embodiment, an air conditioner is typically used for a vehicle. FIG. 1 is a schematic diagram showing an air conditioner 1 for a vehicle according to the present embodiment, and FIG. 2 is a block diagram showing an electric controller of the air conditioner in the present embodiment.

The vehicle air conditioner 1 is provided with an interior air conditioning unit 10 shown in FIG. 1, and an air conditioning controller 50 (A/C ECU) shown in FIG. 2. The interior air conditioning unit 10 is located inside of an instrument panel (i.e., dash panel) positioned at the frontmost portion in a vehicle compartment. The interior air conditioning unit 10 includes an air conditioning casing 11 forming an outer shell and defining therein the air passage. In the air conditioning casing 11, a blower 12, an evaporator 13, a heater core 14 and the like are disposed.

The casing 11 defines the air passage through which air flows into the vehicle compartment. The casing 11 is made of a resin (e.g., polypropylene) having a suitable elasticity and being superior in the strength. An inside/outside air switching box 20 is located at the most upstream side to selectively introduce inside air or/and outside air into the casing 11. Hear, inside air is air inside the vehicle compartment, outside air is air outside the vehicle compartment.

More specifically, the inside/outside air switching box 20 is provided with an inside air introduction port 21 for introducing inside air into the casing 11, and an outside air introduction port 22 for introducing outside air into the casing 11. An inside/outside air switching door 23 is disposed in the inside/outside air switching box 20 to continuously adjust open areas of the inside air introduction port 21 and the outside air introduction port 22. Therefore, the inside/outside air switching door 23 can adjust a ratio between a flow amount of inside air (i.e., air inside the vehicle compartment) introduced from the inside air introduction port 21 and a flow amount of outside air (i.e., air outside the vehicle compartment).

Thus, the inside/outside air switching door 23 is adapted as a suction mode changing portion for switching an air suction mode by changing a ratio between the flow amount of inside air introduced into the casing 11 via the inside air introduction port 21 and the flow amount of outside air introduced into the casing 11 via the outside air introduction port 22. The inside/outside air switching door 23 is driven by an electrical actuator 62 shown in FIG. 2, and operation of the electrical actuator 62 is controlled by a control signal output from the air conditioning controller 50.

The blower 12 is disposed in the casing 11 at a downstream air side of the inside/outside air switching box 20, to blow air drawn via the inside/outside air switching box 20 toward the interior of the vehicle compartment. The blower 12 is an electrical blower having a centrifugal multi-blade fan (e.g., sirocco fan) 12 a and an electrical motor 12 b, for example. In this case, the centrifugal multi-blade fan 12 a is driven by the electrical motor 12 b, and the rotational speed (air blowing amount) of the electrical motor 12 b is controlled by a control voltage output from the air conditioning controller 50.

The evaporator 13 and the heater core 14 are disposed in the casing 11 at a downstream air side of the blower 12, to adjust the temperature of air to be blown into the vehicle compartment.

The evaporator 13 is a cooling heat exchanger in which the refrigerant passing therein is heat-exchanged with air blown by the blower 12 to cool the blown air. The evaporator 13 is one component in a refrigerant cycle (not shown) that includes a compressor, a condenser, a gas-liquid separator, an expansion valve, in addition to the evaporator 13.

The compressor is disposed in an engine compartment to draw refrigerant, to compress the drawn refrigerant and to discharge the compressed refrigerant. For example, the compressor is an electrical compressor in which a fixed-displacement compression mechanism with a fixed discharge capacity is driven by an electrical motor. The electrical motor is an alternate motor, in which its operation (e.g., rotation speed) is controlled by an alternate voltage output from an inverter 61.

The inverter 61 outputs an alternate voltage of a frequency in accordance with a control signal output from the air conditioning controller 50 (A/C ECU) described later. A refrigerant discharge capacity of the compressor is changed by controlling its rotation speed. The compressor may be driven by an engine (not shown) that outputs a drive power for a vehicle running.

The condenser is arranged in the engine compartment. Outside air sent from an outdoor fan 63 is heat exchanged with refrigerant. Thus, the compressed refrigerant is cooled and condensed so as to become in a liquid phase. The outdoor fan 63 is an electrical fan, in which its rotational speed (air blowing amount) is controlled by a control voltage output from the air conditioning controller 50. That is, an operation ratio of the outdoor fan 63 is controlled by the air conditioning controller 50.

The gas-liquid separator is configured to flow therein the cooled and condensed refrigerant from the condenser, and to separate the refrigerant into gas refrigerant and liquid refrigerant. The gas-liquid separator has a liquid refrigerant outlet from which only liquid refrigerant separated in the gas-liquid separator flows to a downstream side. The expansion valve is a decompressing portion to decompress and expand the liquid refrigerant. The evaporator 13 is adapted to evaporate the decompressed refrigerant by performing heat exchange between refrigerant and air.

The casing 11 has an air passage such as a first air passage 15 and a second air passage 16, and a mixture space 17. The air passage such as the first air passage 15 and the second air passage 16 is arranged downstream of the evaporator 13 in the air flow direction, so that air passing through the evaporator 13 flows through the first air passage 15 and the second air passage 16. Air passing through the first air passage 15 and air passing through the second air passage 16 while bypassing the first air passage 15 are mixed in the mixture space 17, so that conditioned air having a desired temperature can be obtained in the mixture space 17.

In the first air passage 15, the heater core 14 is arranged as a heating portion, so that air dehumidified and cooled by the evaporator 13 flows through the heater core 14 through the first air passage 15. The heater core 14 is a heating heat exchanger configured to perform heat exchange between engine coolant (hot water) heated by heat of the vehicle engine and air after passing through the evaporator 13. Thus, the heat core 14 heats air after passing through the evaporator 13 in the first air passage 15.

Specifically, a coolant passage (not shown) is provided between the heater core 14 and the engine thereby configuring a coolant circuit (now shown) in which coolant is circulated between the heater core 14 and the engine. An electric water pump (not shown) is arranged in the coolant circuit so as to circulate the coolant between the engine and the heater core 14.

On the other hand, cool air having passed through the evaporator 13 flows into the mixture space 17 through the second air passage 16 used as the cool air bypass passage while bypassing the heater core 14. Therefore, the temperature of air in the mixture space 17 is changed by a ratio of air passing through the first air passage 15 and air passing through the second air passage 16.

In the present embodiment, an air mix door 18 is located downstream of the evaporator 13 at an inlet side of the first and second air passages 15, 16, so as to continuously change an air flow ratio flowing into the first and second air passages 15, 16.

Therefore, the air mix door 18 is adapted as a temperature controlling portion to control a temperature of air in the mixture space 17 (a temperature of air to be sent into the vehicle compartment). The air mix door 18 is driven by an electrical actuator 64, and operation of the electrical actuator 64 is controlled by a control signal output from the air conditioning controller 50.

Furthermore, at the most downstream air side, the casing 11 is provided with plural air outlets 24, 25, 26 from which conditioned air of the mixture space 17 is blown into the vehicle compartment that is a space to be air-conditioned. The plural air outlets 24, 25, 26 are a defroster air outlet 24, a face air outlet 25 and a foot air outlet 26.

The defroster air outlet 24 is provided to blow conditioned air toward an inner surface of a windshield of the vehicle. The face air outlet 25 is provided to blow conditioned air toward an upper side of a passenger seated on a seat of the vehicle compartment. The foot air outlet 26 is provided to blow conditioned air toward a lower side of the passenger seated on the seat of the vehicle compartment.

Doors 27, 28 are arranged at upstream air sides of the air outlets 24 to 26, to switch an air outlet mode. For example, a defroster/face door 27 and a foot door 28. are arranged as an air-outlet mode changing portion.

The defroster/face door 27 is disposed to adjust open areas of the defroster air outlet 24 and the face air outlet 25. The foot door 28 is disposed to adjust an open area of the foot air outlet 26.

The doors 27, 28 are operatively linked by an electric actuator 65 through a non-illustrated link mechanism, for example. The operation of the electrical actuator 65 for the air-outlet mode switching portion is controlled by a control signal output from the air conditioning controller 50.

The air outlet mode includes a face mode, a bi-level mode, a foot mode and a foot/defroster mode. In the face mode, the face air outlet 25 is fully opened so that conditioned air is blown toward the upper side of the passenger in the vehicle compartment from the face air outlet 25. In the bi-level mode, both the face air outlet 25 and the foot air outlet 26 are opened so that conditioned air is blown toward the upper and lower sides of the passenger in the vehicle compartment. In the foot mode, the foot air outlet 26 is fully opened and the defroster air outlet 24 is opened by a small open degree so that conditioned air is mainly blown from the foot air outlet 26. In the foot/defroster mode, the foot air outlet 26 and the defroster air outlet 24 are opened by approximately same open degree (e.g., half open degree), so that conditioned air is blown from both the foot air outlet 26 and the defroster air outlet 24.

Next, an electrical control portion of the present embodiment will be described with reference to FIG. 2. The air conditioning controller 50 includes a microcomputer and a circumference circuit. The microcomputer has CPU, ROM, RAM, etc. The air conditioning controller 50 performs various calculations and processes based on control programs stored in the ROM, and performs control operation of various equipments connected to output of the air conditioning controller 50. For example, operation of the blower 12, the inverter 61, the outdoor fan 63 and the electrical actuators 62, 64, 65 and the like is controlled by the air conditioning controller 50.

A sensor group is connected to an input side of the air conditioning controller 50. For example, the sensor group includes an inside air sensor 51 adapted to detect a temperature Tr of the vehicle compartment, an outside air sensor 52 adapted to detect an outside air temperature Tam, a solar sensor 53 adapted to detect a solar radiation amount Ts entering into the vehicle compartment, a discharge temperature sensor 54 adapted to detect a refrigerant temperature Td discharged from the compressor 31, a discharge pressure sensor 55 adapted to detect a refrigerant pressure Pd discharged from the compressor 31, an evaporator temperature sensor 56 adapted to detect an air temperature TE flowing out of the evaporator 13, a suction temperature sensor 57 adapted to detect a refrigerant temperature Tsi drawn into the compressor 31, and a coolant temperature sensor 58 adapted to detect an engine coolant temperature TW, and the like.

In the present embodiment, the evaporator temperature sensor 56 is disposed to detect a fin temperature of a heat exchanging portion of the evaporator 13. The air temperature TE flowing out of the evaporator 13 is a temperature corresponding to the refrigerant evaporation temperature in the evaporator 13. Therefore, as the evaporator temperature sensor 56, an air temperature detector located at a portion of the evaporator 13 other than the heat exchanging fin may be used, or a temperature detector for detecting a temperature of the refrigerant flowing in the evaporator 13 may be used.

Furthermore, a wet-state detection sensor 59 is provided to detect a wet state of the evaporator 13 due to condensation water. The detection signal of the wet-state detection sensor 59 is input to an input side of the air conditioning controller 50. As the wet-state detection sensor 59, a condensation water sensor for directly detecting condensation water on the evaporator 13 may be used.

Alternatively, a temperature-humidity sensor for detecting an evaporator temperature and an air humidity may be used as the wet-state detection sensor 5 a. In a case where the temperature-humidity sensor is used as the wet-state detection sensor 59, the air conditioning controller 50 calculates a dew point temperature, and determines that condensation water exists on the evaporator 13 when the detected temperature of the temperature-humidity sensor is lower than the dew point temperature. In this case, the air conditioning controller 50 is adapted as a determination portion for determining whether the condensation water exists on the evaporator 13 based on the detection value of the temperature-humidity sensor as the wet-state detection sensor 59.

An operation panel 60 is located near the instrument panel at the front portion of the vehicle compartment. The operation panel 60 is connected to the input side of the air conditioning controller 50, such that operation signals of various air-conditioning operation switches provided in the operation panel 60 are input to the input side of the air conditioning controller 50. The air-conditioning operation switches provided in the operation panel 60 include, for example, an operation switch (not shown) of the air conditioner, an air-conditioning switch 60 a for selectively turning on or off of the compressor thereby turning on or off of the air conditioning operation in the air conditioner, an automatic switch 60 b for setting or releasing an automatic control of the air conditioner, an operation mode selecting switch (not shown) for selecting an operation mode, an air suction mode selecting switch 60 c for selectively switching an air suction mode, an air outlet mode selecting switch (not shown) for selectively switching an air outlet mode, an air amount setting switch (not shown) for setting an air blowing amount of the blower 12, a temperature setting switch 60 d for setting a temperature of the vehicle compartment, and the like.

Next, arrangement positions of the evaporator temperature sensor 56 and the wet-state detection sensor 59 are described. FIG. 3 is a schematic sectional view showing a part of the interior air conditioning unit 10, and FIG. 4 shows temperature distributions on the evaporator 13. FIG. 5A is a front view showing a part of the evaporator 13 when being viewed from a downstream air side of the evaporator 13, and FIG. 5B is an enlarged sectional view showing a part of the evaporator 13 shown in FIG. 5A.

As shown in FIG. 3, the evaporator 13 is arranged in the casing 11 to across an entire area of the air passage of the casing 11 and to have an air inlet surface 13 a and an air outlet surface 13 b substantially perpendicular to an air flow direction. In the example of FIG. 3, air flows in a horizontal direction in the casing 11, and thereby the air inlet surface 13 a and the air outlet surface 13 b extend in a direction (e.g., vertical direction) perpendicular to the horizontal direction. The air inlet surface 13 a and the air outlet surface 13 b of the evaporator 13 may be tilted with respect to the vertical direction in FIG. 3. A drain port 11 a is provided in a bottom surface portion of the casing 11 to discharge condensation water W generated on the evaporator 13 to outside of the vehicle compartment. In the example of FIG. 3, the drain port 11 a is provided at a position of the bottom surface portion of the casing 11, immediately downstream of the evaporator 13.

As shown in FIG. 4, the evaporator 13 includes a heat exchanging core portion 131, and tank portions 132, 133 extending horizontally and positioned at upper and lower sides of the heat exchanging core portion 131. Furthermore, the evaporator temperature sensor 56 and the wet-state detection sensor 59 are attached to the air outlet surface 13 b of the heat exchanging core portion 131 of the evaporator 13.

The heat exchanging core portion 131 includes a plurality of tubes 131 a extending in a tube longitudinal direction (top-bottom direction in FIG. 3), in which refrigerant flows in the top-bottom direction. A fluid (e.g., air) to be cooled passes through the heat exchanging core portions 131, between adjacent tubes 131 a.

Corrugated fins 131 b are arranged between the tubes 131 a to facilitate heat exchange between the refrigerant flowing inside of the tubes 131 a and air passing outside of the tubes 131 a. The tubes 131 a and the fins 131 b are alternately stacked in a stack direction (e.g., left-right direction in FIG. 5A), thereby forming the heat exchanging core portion 131.

The tubes 131 a may be flat tubes having flat surfaces along the air flow direction. The fin 131 b may be formed by bending a plate member in a wave shape and may be made of aluminum. The fins 131 b are attached to facilitate heat exchange between the refrigerant flowing therein and the air flowing outside of the tubes 131 a.

In the example of FIG. 3, the wet-state detection sensor 59 is attached to the air outlet surface 13 b of the heat exchanging core portion 131 at a position where the temperature of the refrigerant is higher than an average temperature of the air outlet surface 13 b. Furthermore, the wet-state detection sensor 59 is located at a position in an upper half portion in the top-bottom direction. The temperature of air passing through the heat exchanging core portion 131 becomes lower from a side of the air inlet surface 13 a of the heat exchanging core portion 131 to a side of the air outlet surface 13 b of the heat exchanging core portion 131, and thereby condensation water will be easily caused on the air outlet surface 13 b of the heat exchanging core portion 131.

As shown in FIG. 4, a temperature distribution is caused on the heat exchanging core portion 131. The temperature distribution is caused, because the refrigerant flowing in the evaporator 13 absorbs heat from air and the temperature of the refrigerant is increased gradually as toward downstream, or because a flow distribution is caused in air passing through the evaporator 13 due to the inner shape of the interior air conditioning unit 10. More specifically, the refrigerant flowing in the evaporator 13 absorbs heat from air, thereby increasing the temperature of the refrigerant as toward downstream in the evaporator 13. Therefore, on the air outlet surface 13 b of the evaporator 13, the temperature becomes highest at the most downstream side in the refrigerant flow of the heat exchanging core portion 131. For example, on the air outlet surface 13 b of the heat exchanging core portion 131 of the evaporator 13, the highest temperature area is the refrigerant downstream area of the tubes 131, flowing from the tubes 131 to the tank portions 132, 133, or a superheat area of the heat exchanging core portion 131, in which the refrigerant becomes in the gas state. In addition, the evaporator 13 tends to get dry easily, as the flow speed of the air passing through the evaporator 13 becomes early. For example, the evaporator 13 may be tilted by an angle with respect the horizontal direction, such that air flows horizontally toward the air inlet surface 13 a of the evaporator 13 in first, and passes through the evaporator 13 in the vertical direction by changing the air flow direction, as shown in the example of FIG. 9. In this case, the flow speed of air passing through the evaporator 13 becomes higher as toward the right side of FIG. 9, far from an air introduction side of the casing 11, and thereby the evaporator 13 is easy to get dry at the right side of FIG. 9.

In the present embodiment, as shown in FIG. 4, the evaporator temperature sensor 56 is arranged at a low temperature area of the air outlet surface 13 b of the heat exchanging core portion 131 lower than the average temperature of the air outlet surface 13 b, because frost prevention control of the evaporator 13 is performed based on the detection temperature of the evaporator temperature sensor 56. By arranging the evaporator temperature sensor 56 at the low evaporator temperature area, it can accurately prevent the whole area of the evaporator 13 from being frosted.

Because the wet-state detection sensor 59 is used for performing a dry prevention control of the evaporator 13, the wet-state detection sensor 59 is arranged at a high temperature area of the air outlet surface 13 b of the heat exchanging core portion 131 of the evaporator 13. Specifically, the wet-state detection sensor 59 is arranged at a high temperature position higher than the average temperature on the air outlet surface 13 b of the heat exchanging core portion 131. As an example, the wet-state detection sensor 59 is arranged at the highest position on the air outlet surface 13 b of the heat exchanging core portion 131 of the evaporator 13.

As shown in FIGS. 5A and 5B, the wet-state detection sensor 59 includes a cylindrical sensor body portion 59 a, and protrusion portions 59 b inserted into clearances between the tubes 131 a and the fins 131 b of the heat exchanging core portion 131.

The protrusion portions 59 b are inserted into the heat exchanging core portion 131 while the fins 131 b are pressed and enlarged by the protrusion portions 59 b, so that the wet-state detection sensor 59 is fixed to the heat exchanging core portion 131. In the present embodiment, the cylindrical sensor body portion 59 a is also inserted into the inner portion of the heat exchanging core portion 131 to detect the wet state.

Next, the operation of the present embodiment with the above configuration will be described with reference to FIGS. 6 and 7. FIG. 6 is a flow chart illustrating a control of the vehicle air conditioner.

First, at step S1, initialization of a flag, a timer, a control variable, and an initial position setting of a stepping motor in respective electrical motors, and the like are performed.

In next step S2, an operation signal is read from the operation panel 60, and then the operation proceeds to step S3. Specifically, the operation signals include a vehicle interior setting temperature Tset set by the vehicle interior temperature setting switch 60 d, a selection signal of the air outlet mode, a selection signal of the air suction mode, a setting signal of the amount of air blown by the blower 12, and the like.

At step S3, signals regarding the, circumstances of the vehicle used for the air conditioning control, that is, detection signals from the above group of sensors 51 to 59 are read, and then the operation proceeds to step S4. At step S4, a target temperature TAO of air to be blown into the vehicle compartment is calculated. The target temperature TAO is computed by the following expression F1.

TAO=Kset×Tset−Kr×Tr−Kam×Tam−Ks×Ts+C   (F1)

Here, Tset is a vehicle interior setting temperature set by the vehicle interior temperature setting switch 60 d, Tr is an inside air temperature detected by the inside air sensor 51, Tam is an outside air temperature detected by the outside air sensor 52, and Ts is an amount of solar radiation detected by the solar radiation sensor 53. Furthermore, Kset, Kr, Kam and Ks are gains, and C is a constant value for a correction.

Next, at step S5 to S11, control states of various components connected to the air conditioning controller 50 are respectively determined.

Specifically at step S5, a target open degree SW of the air mix door 18 is calculated based on the calculated TAO, a temperature TE of air blowing from the evaporator 13 and detected by the evaporator temperature sensor 56, and an engine coolant temperature TW detected by the coolant temperature sensor 58. Specifically, the target open degree SW is computable with the following expression F2.

SW=[(TAO−TE)/(TW−TE)]×100 (%)   (F2)

Here, SW=0 (%) represents the maximum cooling position of the air mixing door 18, at which the second air passage 16 as the cool air bypass passage is fully opened, and the first air passage 15 is fully closed. In contrast, SW=100 (%) represents the maximum heating position of the air mixing door 18. At the maximum heating position, the second air passage 16 as the cool air bypass passage is fully closed, and the first air passage 15 is fully opened.

At step S6, a target air-blowing amount of the blower 12 is determined. Specifically, a voltage applied to the blower motor 12 b is set based on the TAO determined at S4, in accordance with a control map memorized in the air conditioning controller 50.

The voltage is increased approximately to the maximum value when a value of the TAO is in a low temperature area (maximum cooling region) and a high temperature area (maximum heating region). Thus, in the maximum cooling region and the maximum heating region, the air amount of the blower 12 is increased into the maximum value. The control map for determining the blower voltage is set, such that the blower voltage is gradually reduced in accordance with an increase of the TAO when the TAO is increased toward a middle temperature area from the low temperature area, thereby gradually reducing the air blowing amount of the blower 12.

Furthermore, the control map for determining the blower voltage is set, such that the blower voltage is gradually reduced in accordance with a reduce of the TAO when the TAO is reduced toward the middle temperature area from the high temperature area, thereby gradually reducing the air blowing amount of the blower 12. When the TAO is in the middle temperature area in the control map, the blower voltage is set at a lowest value so that the air blowing amount of the blower 12 becomes at a lowest value.

At step S7, an air suction mode is determined based on a switching state of the inside/outside air switching box 23. Specifically, the air suction mode is determined by using a control map stored in the air conditioning controller 50 based on the TAO. Generally, the inside/outside air switching box 20 is switched to preferentially set the outside air mode for introducing outside air. However, for example, in a case where a high cooling performance is required in an extremely low temperature area of the TAO, the inside air mode is selected so as to introduce the inside air into the inside/outside air switching box 20. Furthermore, an exhaust gas concentration detection detector may be provided to detect an exhaust gas concentration of outside air. In this case, when exhaust gas concentration of outside air becomes more than a predetermined standard concentration, the inside air mode is selected.

Next, at step S8, an air outlet mode is determined. Specifically, the air outlet mode is determined by using a control map stored in the air conditioning controller 50 based on the TAO. In this embodiment, the air outlet mode is changed in this order of the foot mode, the bi-level mode, the face mode as the TAO is increased from a low temperature region to a high temperature region. Therefore, the face mode is selected mainly for the summer, the bi-level mode is selected mainly for the spring and the autumn, the foot mode is selected mainly for the winter. Furthermore, when there is high possibility that fogging will occur on a window based on a detection value of a humidity sensor, the foot defroster mode or a defroster mode may be selected.

At step S9, a refrigerant discharge capacity of the compressor is determined. For example, a target evaporator temperature TEO for the evaporator 13 is determined. The target evaporator temperature TEO is a target temperature of an air temperature TE flowing out of the evaporator 13, for example. For example, a deviation En (TEO-TE) is computed between the target evaporator temperature TEO and the evaporator air temperature TE, and the rotation speed of the compressor may be determined based on the deviation En.

Then, at step S10, control signals are output from the air conditioning controller 50 to various air-conditioning control equipments 12, 61-65, such that the control states determined at steps S5 to S9 can be obtained. For example, the compressor is controlled so as to be operated with a rotational speed determined at step S9. At step S11, the control operation is kept for a control cycle period τ. When the control cycle period τ is determined to elapse, the operation returns to step S2. For example, the control period τ is set at a control period (e.g., 250 ms) later as compared with an engine control. Even if the control period is long, controllability of the air conditioning control is not affected, compared with the engine control etc. Further, the volume of communication for the air conditioning control in the vehicle interior is restricted, and thus the volume of communication in a control system which needs to perform the high-speed control can be sufficiently ensured, as in the engine control or the like.

Next, the control process of step S9 of FIG. 6, for determining the target evaporator temperature TEO, will be described in detail. FIG. 7 is a time chard for determining the target evaporator temperature TEO, in accordance with an operation time. When the engine (E/G) starts its operation, the air conditioning controller 50 causes the compressor to be operated so that low-temperature and low-pressure refrigerant flows into the evaporator 13. Therefore, air can be cooled by the evaporator 13.

For example, an initial value of the target evaporator temperature TEO of air flowing from the evaporator 13 is determined based on the target air temperature TAO determined at step S4 by using a control map stored in the air conditioning controller 50. The control map is set such that the target evaporator temperature TEO becomes lower, as the target air temperature TAO becomes lower, that is, as a cooling load in the vehicle compartment becomes higher.

When the compressor rotational speed is determined based on the initial value of the target evaporator temperature TEO, and the compressor is operated with the compressor rotational speed, the temperature of the evaporator 13 gradually decreases. Then, when the temperature of the evaporator 13 is decreased lower than the dew point temperature, the evaporator 13 will begin to be wetted.

When condensation water is generated on the evaporator 13 and a wet state of the evaporator 13 is detected by the wet-state detection sensor 59, the air conditioning controller 50 increases the target evaporator temperature TEO by a predetermined value (e.g., 0.5° C.). Thus, the temperature of the evaporator 13 is also increased.

As the target evaporator temperature TEO increases gradually, the temperature of the evaporator 13 is increased to become equal to or higher than the dew point temperature. When the temperature of the evaporator 13 is increased to become equal to or higher than the dew point temperature, the condensation water is dried. At this time, the wet of the evaporator 13 cannot be detected by the wet-state detection sensor 59, and a dry state can be output from the wet-state detection sensor 59.

At this time, the air conditioning controller 50 sets the target evaporator temperature TEO at a predetermined value (e.g., 0.5° C.). By gradually decreasing the target evaporator temperature TEO, the temperature of the evaporator 13 becomes equal to or lower than the dew point temperature, and thereby the condensation water may be generated gain.

By repeating the above control of the air conditioning controller 50, the temperature of the evaporator 13 becomes approximately equal to or lower than the dew point temperature. As described above, even in this case, the temperature distribution is caused in the evaporator 13. In FIG. 7, TE1 indicates an evaporator temperature in a high-temperature portion of the evaporator 13, TE2 indicates an evaporator temperature in a middle-temperature portion of the evaporator 13, and TE3 indicates an evaporator temperature in a low-temperature portion of the evaporator 13.

As described above, in the present embodiment, the wet-state detection sensor 59 is located in the high-temperature portion of the evaporator 13, in which condensation water begins to get dry early. That is, the dry of the condensation water starts at an early time, in the high-temperature portion of the evaporator 13 as in the graph TE1, as compared that in the graphs TE2, TE3. Thus, it can determine that the entire area of the air outlet surface 13 b of the heat exchanging core portion 131 from being wetted, when the wet state is detected by the wet-state detection sensor 59. Therefore, by using the detection value of the wet-state detection sensor 59, it can prevent the evaporator 13 from being dried, in the entire area of the air outlet surface 13 b.

That is, the wet-state detection sensor 59 is arranged at a position of the air outlet surface 13 b of the evaporator 13, at which condensation water is easy to get dry. That is, an easy drying degree of the condensation water may be determined based on the temperature of the air outlet surface 13 b of the evaporator 13. When the temperature in a part of the air outlet surface 13 b of the evaporator 13 is higher than the average temperature of the air outlet surface 13 b of the evaporator 13, the easy drying degree at the part of the air outlet surface 13 b of the evaporator 13 is increased.

Thus, in the vehicle air conditioner provided with the evaporator 13 and the wet-state detection sensor 59, the target evaporator temperature TEO is controlled as in the graph of FIG. 7, and thereby the evaporator temperature TE can be controlled so that the entire surface area of the evaporator 13 becomes accurately in the wet state. Therefore, it can accurately prevent bad-smell from being caused from the evaporator 13, while the evaporator temperature TE is increased as much as possible.

FIGS. 8A and 8B show a modification example of the present embodiment, and respectively correspond to the example of FIGS. 5A and 5B. In the example of FIGS. 8A and 8B, the cylindrical sensor body portion 59 a of the wet-state detection sensor 59 is not inserted into the inner portion of the heat exchanging core portion 131, but is arranged to be parallel with the air outlet surface 13 b of the heat exchanging core portion 131. More specifically, the wet-state detection sensor 59 includes the cylindrical body portion 59 a arranged in parallel with the air outlet surface 13 b of the heat exchanging core portion 131, and the protrusion portions 59 b protruding into the clearance between the tubes 131 a and the corrugated fins 131 b to be fixed into the inner portion of the evaporator 13. Even in the modification example, as described above, the evaporator temperature TE can be controlled so that the entire surface area of the evaporator 13 becomes accurately in the wet state. In the above described embodiment, the air inlet surface 13 a and the air outlet surface 13 b of the evaporator 13 extend in the top-bottom direction perpendicular to the horizontal direction. However, the air inlet surface 13 a and the air outlet surface 13 b of the evaporator 13 may extent in a direction tilted by an angle larger than 5 degrees with respect to the horizontal direction.

Second Embodiment

A second embodiment of the present invention will be described with reference to FIG. 9. As shown in FIG. 9, in the second embodiment, the evaporator 13 is arranged in the casing 11 approximately horizontally, so that air passes through the evaporator 13 upwardly from a lower side of the evaporator 13. Specifically, the air inlet surface 13 a and the air outlet surface 13 b of the evaporator 13 are tilted with respect to the horizontal direction by an angle larger than 5 degrees. Even in this case, draining performance of the condensation water W generated on the heat exchanging core portion 131 can be improved.

In the arrangement of the evaporator 13 shown in FIG. 9, the air outlet surface 13 b of the heat exchanging core portion 131 is positioned at an upper side of the evaporator 13, and the air inlet surface 13 a of the heat exchanging core portion 131 is positioned at a lower side of the evaporator 13. Even in this case, the air outlet surface 13 b of the heat exchanging core portion 131 can be wetted by the condensation water W. In the arrangement of FIG. 9, because the condensation water W of the heat exchanging core portion 131 is pushed toward the air outlet surface 13 b of the evaporator 13, the air outlet surface 13 b of the heat exchanging core portion 13 can be easily wetted.

In the example of FIG. 9, the condensation water W flows along the inclination of the air outlet surface 13 b of the heat exchanging core portion 13, and flows downwardly in the top-bottom direction, and then is discharged from the drain port 11 a. Thus, the amount of the condensation water W becomes smaller, as the position of the air outlet surface 13 b of the evaporator 13 becomes upper. That is, condensation water begins to get dry easily as the position of the air outlet surface 13 b becomes higher.

Thus, in the present embodiment, the wet-state detection sensor 59 is attached to an upper side on the air outlet surface 13 b of the heat exchanging core portion 131, upper than a middle portion of the air outlet surface 13 b of the heat exchanging core portion 31 in the top-bottom direction. Thus, similarly to the above-described first embodiment, the evaporator temperature TE can be controlled, so that the entire surface area of the evaporator 13 becomes accurately in the wet state while the evaporator temperature TE is increased as much as possible.

That is, even in the present embodiment, the wet-state detection sensor 59 is arranged at an easy drying position of the air outlet surface 13 b of the evaporator 13, at which condensation water is easy to get dry. In the second embodiment, the easy drying position of the air outlet surface 13 b of the evaporator 13 is an upper half area of the air outlet surface 13 b of the evaporator 13, for example. Furthermore, the easy drying position of the air outlet surface 13 b of the evaporator 13 is a high temperature area on the air outlet surface 13 b of the evaporator 13, higher than the average temperature. That is, the wet-state detection sensor 59 is arranged at a position of the air outlet surface 13 b, in which a determination value for indicating an easy drying degree satisfies a predetermined condition so that the condensation water is easy to get dry.

Thus, when the wet-state detection sensor 59 is arranged at a position higher than the average temperature in the upper half area of the air outlet surface 13 b of the heat exchanging core portion 131, the entire surface area of the evaporator 13 can be accurately made in the wet state by using the detection value of the wet-state detection sensor 59.

When there is no the high temperature portion higher than the average temperature in the upper half area of the air outlet surface 13 b of the heat exchanging core portion 131, that is, when the high temperature position higher than the average temperature is positioned in the lower half area of the air outlet surface 13 b of the heat exchanging core portion 131, the wet-state detection sensor 59 is arranged in the upper half area of the air outlet surface 13 b of the heat exchanging core portion 131. It is because the upper half position of the air outlet surface 13 b of the evaporator 13 easy begins to get dry, as compared with the high-temperature position, in the arrangement of the evaporator 13 shown in FIG. 9.

Other Embodiments

(1) In the above-described first embodiment, the target evaporator temperature TEO is gradually increased or decreased based on the detection value of the wet-state detection sensor 59. However, a humidity sensor may be arranged at the same position as that of the wet-state detection sensor 59, instead of the wet-state detection sensor 59. In this case, the target evaporator temperature TEO may be determined based on a detection value of the humidity sensor such that the relative humidity on the evaporator 13 can be maintained always at 100% RH.

(2) In the above-described embodiments, as the cooling heat exchanger, the evaporator 13 of the refrigerant cycle is used. However, the present invention may be applied to various-type cooling heat exchangers. For example, the present invention can be suitably applied to a cooling heat exchanger, in which air is cooled by performing heat exchange between a low-temperature coolant and air. That is, in the air conditioner in which an air outlet surface 13 b of the cooling heat exchanger is arranged by an angle larger than a predetermined angle (e.g., 5° C.) with respect to the horizontal direction, if the wet-state detection sensor 59 is positioned in the upper half area of the air outlet surface 13 b of the cooling heat exchanger, the other parts may be suitably changed. For example, the structure of the cooling heat exchanger is not limited to the evaporator 13 described in the embodiments and modification examples thereof, and may be changed to the other structure. According to the above embodiments and modifications thereof, because the wet-state detection sensor 59 is located in the easy drying position of the air outlet surface 13 b of the cooling heat exchanger, in which the condensation water begins to get easy dry. Therefore, the wet state can be accurately set in the entire surface area of the cooling heat exchanger while the temperature of the cooling heat exchanger is increased as much as possible.

(3) The air conditioner of the present invention may be used for a vehicle which is driven by a drive force from an engine, or may be used for a vehicle such as a fuel cell vehicle and an electrical vehicle.

Alternatively, the air conditioner may be mounted to a parallel type hybrid vehicle in which the drive force can be directly obtained from both the engine and the electrical motor, or a serial type hybrid vehicle, in which the engine EG is used as a drive source of the electric motor, the generated power charges a battery, and the electric motor is activated by the power of the battery. The serial type hybrid vehicle drives by obtaining driving force from the electric motor.

(4) In the above-described embodiments, the air conditioner is used for a vehicle. However, the air conditioner may be suitably used for a fixed type.

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

1. An air conditioner comprising: a cooling heat exchanger configured to cool air, the cooling heat exchanger including an air outlet surface from which air flows out of the cooling heat exchanger; and a wet-state detection sensor attached to the air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water, wherein the air outlet surface of the cooling heat exchanger is tilted by an angle with respect to a horizontal direction or is perpendicular to the horizontal direction, and the wet-state detection sensor is arranged at a position in an upper half area of the air outlet surface.
 2. An air conditioner comprising: a cooling heat exchanger configured to cool air, the cooling heat exchanger including an air outlet surface from which air flows out of the cooling heat exchanger; and a wet-state detection sensor attached to the air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water, wherein the wet-state detection sensor is arranged at a position of the air outlet surface in a high-temperature area in which the temperature is higher than an average temperature of the air outlet surface.
 3. The air conditioner according to claim 1, wherein the upper half area of the air outlet surface of the cooling heat exchanger has a high-temperature area in which the temperature is higher than an overage temperature of the air outlet surface, and the wet-state detection sensor is arranged at a position in the high-temperature area.
 4. The air conditioner according to claim 1, wherein the wet-state detection sensor is a moisture sensor adapted to detect moisture.
 5. The air conditioner according to claim 1, wherein the wet-state detection sensor is a temperature-humidity sensor adapted to detect temperature and humidity of air flowing out of the air outlet surface, the air conditioner further comprising a control portion adapted to calculate a dew point temperature based on a detected value of the wet-state detection sensor, and determines that the air outlet surface is, wetted by the condensation water when a detected temperature of the wet-state detection sensor is lower than the dew point temperature.
 6. An air conditioner comprising: a cooling heat exchanger configured to cool air, the cooling heat exchanger including an air outlet surface from which air flows out of the cooling heat exchanger; and a wet-state detection sensor attached to the air outlet surface of the cooling heat exchanger to detect a wet state of the air outlet surface due to condensation water, wherein the wet-state detection sensor is arranged at a position of the air outlet surface, in which a determination value for indicating an easy drying degree satisfies a predetermined condition so that the condensation water is easy to get dry.
 7. The air conditioner according to claim 1, wherein the cooling heat exchanger is an evaporator in which refrigerant is evaporated thereby cooling air, the evaporator is one of components of a refrigerant cycle in which the refrigerant is circulated, and operation of the refrigerant cycle is controlled based on detected value of the wet-state detection sensor, such that all the air outlet surface is made in a wet state.
 8. The air conditioner according to claim 7, further comprising an evaporator temperature sensor located in the air outlet surface of the evaporator at a low-temperature area where the temperature of the evaporator is lower than an average temperature, and the wet-state detection sensor is located in the air outlet surface of the evaporator at a high-temperature area where the temperature of the evaporator is higher than the average temperature. 